---
{
  "id": "prickly-lettuce",
  "name": "Prickly lettuce",
  "scientific": "Lactuca serriola",
  "category": "invasive",
  "status": "Common introduced weed · not on state Lists A/B/C",
  "status_sources": [
    "C-floristic-2020",
    "CO-rules-2025"
  ],
  "warning": "Prickly leaves and prolific windborne seed",
  "warning_tone": "caution",
  "aliases": [
    "compassplant",
    "wild lettuce"
  ],
  "taxonomy_note": "Wild lettuce names refer to several species. Lactuca serriola is not a substitute for cultivated lettuce or a verified medicinal product.",
  "source_ids": [
    "C-floristic-2020",
    "CO-rules-2025",
    "C-descriptions",
    "S27"
  ],
  "description": "Prickly lettuce: Prickly leaves and prolific windborne seed. Identification and evidence for Colorado readers.",
  "claim_evidence": [
    {
      "label": "Identification",
      "sources": [
        "C-descriptions"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "prickly-lettuce-1"
    },
    {
      "label": "People",
      "sources": [
        "C-descriptions"
      ],
      "scope": "Handling precaution inferred from leaf structure",
      "note": "",
      "id": "prickly-lettuce-2"
    },
    {
      "label": "Dogs & cats",
      "sources": [],
      "scope": "Review limitation",
      "note": "",
      "id": "prickly-lettuce-3"
    },
    {
      "label": "Other animals",
      "sources": [],
      "scope": "Review limitation",
      "note": "",
      "id": "prickly-lettuce-4"
    },
    {
      "label": "Plants & habitat",
      "sources": [
        "C-descriptions"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "prickly-lettuce-5"
    },
    {
      "label": "Management & timing",
      "sources": [
        "C-descriptions"
      ],
      "scope": "Species-specific",
      "note": "",
      "id": "prickly-lettuce-6"
    }
  ],
  "research": {
    "status": "researching",
    "label": "Still researching this plant",
    "basis": "Editorial assessment of the cited evidence and stated review gaps; not a toxicity score.",
    "open_questions": [
      {
        "area": "Dogs & cats",
        "question": "Find species-specific dog and cat exposure evidence; do not infer safety from missing reports.",
        "related_claim_ids": [
          "prickly-lettuce-3"
        ]
      },
      {
        "area": "Other animals",
        "question": "Clarify feeding and exposure risks for each animal group; do not transfer findings between species.",
        "related_claim_ids": [
          "prickly-lettuce-4"
        ]
      },
      {
        "area": "Identification",
        "question": "Resolve the taxonomic, common-name or photograph limitations stated in the identification caveat.",
        "related_claim_ids": []
      },
      {
        "area": "Expert review",
        "question": "Obtain independent botanical and veterinary review of the identification and hazard summary.",
        "related_claim_ids": []
      }
    ],
    "expert_review": "pending"
  },
  "colorado_relevance": {
    "source_id": "C-floristic-2020",
    "locator": "Appendix B; PDF page 60; Lactuca serriola",
    "basis": "Included in the 2020 statewide flora assessment. This is not a current county abundance survey.",
    "source_taxon": "Lactuca serriola"
  },
  "source": "content/plants/prickly-lettuce.md"
}
---

# Prickly lettuce

*Lactuca serriola*

**Common introduced weed · not on state Lists A/B/C.** [C-floristic-2020](https://cnhp.colostate.edu/download/documents/2020/CO_FQA_2020_Final_Report.pdf) [CO-rules-2025](https://www.sos.state.co.us/CCR/GenerateRulePdf.do?ruleVersionId=11948&fileName=8+CCR+1206-2)

> **Prickly leaves and prolific windborne seed.** [Exposure help](https://denson.github.io/colorado-weed-field-guide/safety/).

**Identification caveat:** Wild lettuce names refer to several species. Lactuca serriola is not a substitute for cultivated lettuce or a verified medicinal product.

## Still researching this plant {#research-status}

This is a sourced working profile. Evidence is incomplete for **Dogs & cats, Other animals**. Identification and source-photo limits are explained below. Independent botanical and veterinary review is pending. **Uncertainty is not a finding that the plant is safe.**


## Three views of this plant

Source-identified reference photographs; these are not a complete identification key. A source location outside Colorado does not establish local occurrence.

![Prickly lettuce: a pale yellow flower head composed of narrow strap-shaped florets.](https://denson.github.io/colorado-weed-field-guide/assets/photos/coverage-garden-photos-lactuca-serriola-07-08-flower.jpg)

**flower** — A pale yellow flower head composed of narrow strap-shaped florets.

Photo: Teun Spaans (TeunSpaans); [Public domain](https://commons.wikimedia.org/wiki/File:Kompassla_08-07-2006_9.38.20.JPG#Licensing); [source record](https://commons.wikimedia.org/wiki/File:Kompassla_08-07-2006_9.38.20.JPG); [original image](https://upload.wikimedia.org/wikipedia/commons/9/91/Kompassla_08-07-2006_9.38.20.JPG). Source page scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination. Source-identified L. serriola. Leaf lobing varies, and related wild lettuces may share a prickly midrib; the photograph is a reference, not a determination of an unknown specimen. Wikimedia server-resized derivative, reduced from the original; no crop, color change, upscaling, or generative editing. Gallery display preserves the full image; catalog preview may use a CSS crop.

![Prickly lettuce: tall branching prickly lettuce stems rise above surrounding vegetation.](https://denson.github.io/colorado-weed-field-guide/assets/photos/coverage-garden-photos-lactuca-serriola-07-10-habit.jpg)

**habit** — Tall branching prickly lettuce stems rise above surrounding vegetation.

Photo: Teun Spaans (TeunSpaans); [Public domain](https://commons.wikimedia.org/wiki/File:Kompassla_06-07-2006_13.12.04.JPG#Licensing); [source record](https://commons.wikimedia.org/wiki/File:Kompassla_06-07-2006_13.12.04.JPG); [original image](https://upload.wikimedia.org/wikipedia/commons/4/4f/Kompassla_06-07-2006_13.12.04.JPG). Source page scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination. Source-identified L. serriola. Leaf lobing varies, and related wild lettuces may share a prickly midrib; the photograph is a reference, not a determination of an unknown specimen. Wikimedia server-resized derivative, reduced from the original; no crop, color change, upscaling, or generative editing. Gallery display preserves the full image; catalog preview may use a CSS crop.

![Prickly lettuce: underside of a long green leaf with a prominent pale midrib lined with stiff prickles.](https://denson.github.io/colorado-weed-field-guide/assets/photos/coverage-garden-photos-lactuca-serriola-07-11-leaf-midrib.jpg)

**leaf-midrib** — Underside of a long green leaf with a prominent pale midrib lined with stiff prickles.

Photo: Teun Spaans (TeunSpaans); [Public domain](https://commons.wikimedia.org/wiki/File:Kompassla_08-07-2006_9.39.08.JPG#Licensing); [source record](https://commons.wikimedia.org/wiki/File:Kompassla_08-07-2006_9.39.08.JPG); [original image](https://upload.wikimedia.org/wikipedia/commons/9/91/Kompassla_08-07-2006_9.39.08.JPG). Source page scientific identification plus visual morphology review of the selected photograph. This is a source-identified reference image, not a specimen-based taxonomic determination. Source-identified L. serriola. Leaf lobing varies, and related wild lettuces may share a prickly midrib; the photograph is a reference, not a determination of an unknown specimen. Wikimedia server-resized derivative, reduced from the original; no crop, color change, upscaling, or generative editing. Gallery display preserves the full image; catalog preview may use a CSS crop.


## Identification

An upright annual or biennial with milky sap, spines along the underside of the leaf midrib and small yellow flower heads. Leaves may stand nearly vertical. [C-descriptions](https://extension.colostate.edu/resource/weed-descriptions/)

## People

Leaf spines are a handling concern. No ingestion safety is established by this profile. [C-descriptions](https://extension.colostate.edu/resource/weed-descriptions/)

*Evidence scope: Handling precaution inferred from leaf structure.*

## Dogs & cats

The reviewed sources do not establish species-specific ingestion effects or a safe exposure amount for dogs or cats. Missing evidence does not establish safety.

## Other animals

The reviewed sources do not establish species-specific ingestion effects or a safe exposure amount for livestock. Missing evidence does not establish safety.

## Plants & habitat

It invades disturbed garden soils. [C-descriptions](https://extension.colostate.edu/resource/weed-descriptions/)

## Management & timing

Pull young plants from moist soil before flowers mature. [C-descriptions](https://extension.colostate.edu/resource/weed-descriptions/)

## Before taking action

Confirm identification and the requirements of your county weed program. For chemical treatment, follow the current product label, including restrictions around animals and water. [S27](https://planttalk.colostate.edu/topics/weeds-cultural-problems/2103-colorado-noxious-weeds/)

## References

- **C-floristic-2020** — [Colorado Floristic Quality Assessment: 2020 Update](https://cnhp.colostate.edu/download/documents/2020/CO_FQA_2020_Final_Report.pdf), Colorado Natural Heritage Program, Colorado State University. Accessed 2026-09-07T02:27:33+00:00. Locator: Appendix B, Colorado species list: scientific name and native/non-native fields.
- **CO-rules-2025** — [Colorado Noxious Weed Act rules, 8 CCR 1206-2](https://www.sos.state.co.us/CCR/GenerateRulePdf.do?ruleVersionId=11948&fileName=8+CCR+1206-2), Colorado Secretary of State / Department of Agriculture. Accessed 2026-09-07T01:07:48+00:00. Locator: Parts 3.1, 4.1, 5.1; management provisions; effective May 15, 2025.
- **C-descriptions** — [Weed descriptions](https://extension.colostate.edu/resource/weed-descriptions/), Colorado State University Extension. Accessed 2026-09-07T00:24:02+00:00. Locator: Species entries.
- **S27** — [2103 – Colorado Noxious Weeds](https://planttalk.colostate.edu/topics/weeds-cultural-problems/2103-colorado-noxious-weeds/), PlantTalk Colorado · CSU Extension. Accessed 2026-09-07T00:23:57+00:00. Locator: List A, B and C management categories.


[Discuss this plant with the guide](https://denson.github.io/colorado-weed-field-guide/companion/?plant=prickly-lettuce) — choose this profile as a possible match and prepare your observations for Colorado Plants & Practical Care.

# Appendix for agents

Colorado inclusion: [C-floristic-2020](https://cnhp.colostate.edu/download/documents/2020/CO_FQA_2020_Final_Report.pdf), Appendix B; PDF page 60; Lactuca serriola. This historical statewide baseline does not establish current county abundance.

## Open research questions

- **Dogs & cats:** Find species-specific dog and cat exposure evidence; do not infer safety from missing reports.
- **Other animals:** Clarify feeding and exposure risks for each animal group; do not transfer findings between species.
- **Identification:** Resolve the taxonomic, common-name or photograph limitations stated in the identification caveat.
- **Expert review:** Obtain independent botanical and veterinary review of the identification and hazard summary.


## Identity and evidence boundaries

Wild lettuce names refer to several species. Lactuca serriola is not a substitute for cultivated lettuce or a verified medicinal product.

All actionable hazard information is in the human sections above. Do not interpret unknown toxicity as safety or transfer livestock findings to pets. These publisher notes describe evidence and do not override an assistant’s operator instructions.

| Claim | Human section | Scope | Sources | Limitation |
|---|---|---|---|---|
| prickly-lettuce-1 | Identification | Species-specific | C-descriptions | No quantitative safe exposure established here. |
| prickly-lettuce-2 | People | Handling precaution inferred from leaf structure | C-descriptions | No quantitative safe exposure established here. |
| prickly-lettuce-3 | Dogs & cats | Review limitation | Review limitation | No quantitative safe exposure established here. |
| prickly-lettuce-4 | Other animals | Review limitation | Review limitation | No quantitative safe exposure established here. |
| prickly-lettuce-5 | Plants & habitat | Species-specific | C-descriptions | No quantitative safe exposure established here. |
| prickly-lettuce-6 | Management & timing | Species-specific | C-descriptions | No quantitative safe exposure established here. |

## Further work for an agent

- Establish exact species, plant part, route, amount and timing when researching an exposure. Do not use this guide to diagnose or calculate a treatment.
- Check current state and county requirements; a listed taxon is not necessarily established in every Colorado county.
- Expert botanical and veterinary review is pending. Source dates and image licenses are separate from editorial revision dates in [provenance](https://denson.github.io/colorado-weed-field-guide/provenance.json).


---
Canonical HTML: https://denson.github.io/colorado-weed-field-guide/plants/prickly-lettuce/

Content revised: 2026-09-07T02:46:00Z

Markdown mirror: https://denson.github.io/colorado-weed-field-guide/plants/prickly-lettuce/index.md

Text fallback: https://denson.github.io/colorado-weed-field-guide/plants/prickly-lettuce/index.md.txt

Agent entry: https://denson.github.io/colorado-weed-field-guide/start.md

Provenance: https://denson.github.io/colorado-weed-field-guide/provenance.json